Identifying and interpreting spatiotemporal variation in diagnoses of infectious syphilis among men, England: 2009 to 2013

OBJECTIVES

Spatial clusters and variations in the trajectory of local epidemics were explored in relation to sexual orientation, demographic factors, stage of syphilis infection and HIV serostatus.

METHODS

Kulldorff's scan statistics (SaTScan) was used to distinguish endemic and temporary clusters using a two-stage analysis.

RESULTS

Endemic areas were found in London, Manchester, Brighton and Blackpool. Up to 40% of diagnoses were found within an 11 km radius of central London. Of men diagnosed with syphilis in London, 80% were men who have sex with men (MSM). Annual incidence in London increased from 24 cases (95% CI 23 to 26) per 100 000 male population in 2009 to 36 cases (95% CI 34 to38) in 2013. In comparison with clusters, endemic areas were characterised by a significantly higher (p<0.05) proportion of MSM (83% compared with 73%), increased HIV positivity (41% vs 15%), age 35 to 44 years (34% vs 23%), a lower proportion of patients born in the UK (50% vs 79%) and a lower proportion of primary stage infection (40% vs 47%). Space-time clusters outside endemic areas occurred in urban and rural areas and diagnoses fluctuated below 10 per month. Exponential increases in diagnoses resembling point source outbreaks were seen at two locations.

CONCLUSION

Control of syphilis in endemic areas has proved elusive and clusters present unique intervention opportunities. Investigating the diversity of local epidemics provides information that can be used to predict outbreak structure, plan and evaluate sexual health services and guide public health investigation, hypothesis generation and research.

Recent outbreaks of infectious syphilis, United Kingdom, January 2012 to April 2014

Six outbreaks of infectious syphilis in the United Kingdom, ongoing since 2012, have been investigated among men who have sex with men (MSM) and heterosexual men and women aged under 25 years. Interventions included case finding and raising awareness among healthcare professionals and the public. Targeting at-risk populations was complicated as many sexual encounters involved anonymous partners. Outbreaks among MSM were influenced by the use of geospatial real-time networking applications that allow users to locate other MSM within close proximity.

An audit of partner notification for syphilis and HIV

Partner notification (PN) is a vital tool used by genitourinary (GU) medicine services in the public health control of sexually transmitted infections. We audited our PN outcomes for syphilis and HIV, over an 18-month period, at the Edinburgh GUM clinic. Follow-up information on testing was only available for 58% of traceable syphilis contacts and 59% of traceable HIV contacts, though substantially larger percentages in each case, respectively 78% and 90%, were informed regarding their risk of exposure. Furthermore, the department achieved screening verification in 78% of identifiable syphilis contacts and 94% of identifiable HIV partners.